/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.MoreObjects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.DoNotMock;

import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Spliterator;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link Table} whose contents will never change, with many other important properties detailed
 * at {@link ImmutableCollection}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
 *
 * @author Gregory Kick
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ImmutableTable<R, C, V> extends AbstractTable<R, C, V>
        implements Serializable
{

    /**
     * Returns a {@code Collector} that accumulates elements into an {@code ImmutableTable}. Each
     * input element is mapped to one cell in the returned table, with the rows, columns, and values
     * generated by applying the specified functions.
     *
     * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
     * if the row, column, or value functions return null on any input.
     *
     * @since 21.0
     */
    public static <T extends @Nullable Object, R, C, V>
    Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(
            Function<? super T, ? extends R> rowFunction,
            Function<? super T, ? extends C> columnFunction,
            Function<? super T, ? extends V> valueFunction)
    {
        return TableCollectors.toImmutableTable(rowFunction, columnFunction, valueFunction);
    }

    /**
     * Returns a {@code Collector} that accumulates elements into an {@code ImmutableTable}. Each
     * input element is mapped to one cell in the returned table, with the rows, columns, and values
     * generated by applying the specified functions. If multiple inputs are mapped to the same row
     * and column pair, they will be combined with the specified merging function in encounter order.
     *
     * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
     * if the row, column, value, or merging functions return null on any input.
     *
     * @since 21.0
     */
    public static <T extends @Nullable Object, R, C, V>
    Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(
            Function<? super T, ? extends R> rowFunction,
            Function<? super T, ? extends C> columnFunction,
            Function<? super T, ? extends V> valueFunction,
            BinaryOperator<V> mergeFunction)
    {
        return TableCollectors.toImmutableTable(
                rowFunction, columnFunction, valueFunction, mergeFunction);
    }

    /**
     * Returns an empty immutable table.
     *
     * <p><b>Performance note:</b> the instance returned is a singleton.
     */
    @SuppressWarnings("unchecked")
    public static <R, C, V> ImmutableTable<R, C, V> of()
    {
        return (ImmutableTable<R, C, V>) SparseImmutableTable.EMPTY;
    }

    /**
     * Returns an immutable table containing a single cell.
     */
    public static <R, C, V> ImmutableTable<R, C, V> of(R rowKey, C columnKey, V value)
    {
        return new SingletonImmutableTable<>(rowKey, columnKey, value);
    }

    /**
     * Returns an immutable copy of the provided table.
     *
     * <p>The {@link Table#cellSet()} iteration order of the provided table determines the iteration
     * ordering of all views in the returned table. Note that some views of the original table and the
     * copied table may have different iteration orders. For more control over the ordering, create a
     * {@link Builder} and call {@link Builder#orderRowsBy}, {@link Builder#orderColumnsBy}, and
     * {@link Builder#putAll}
     *
     * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
     * safe to do so. The exact circumstances under which a copy will or will not be performed are
     * undocumented and subject to change.
     */
    public static <R, C, V> ImmutableTable<R, C, V> copyOf(
            Table<? extends R, ? extends C, ? extends V> table)
    {
        if (table instanceof ImmutableTable)
        {
            @SuppressWarnings("unchecked")
            ImmutableTable<R, C, V> parameterizedTable = (ImmutableTable<R, C, V>) table;
            return parameterizedTable;
        }
        else
        {
            return copyOf(table.cellSet());
        }
    }

    static <R, C, V> ImmutableTable<R, C, V> copyOf(
            Iterable<? extends Cell<? extends R, ? extends C, ? extends V>> cells)
    {
        ImmutableTable.Builder<R, C, V> builder = ImmutableTable.builder();
        for (Cell<? extends R, ? extends C, ? extends V> cell : cells)
        {
            builder.put(cell);
        }
        return builder.build();
    }

    /**
     * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
     * Builder#Builder() ImmutableTable.Builder()} constructor.
     */
    public static <R, C, V> Builder<R, C, V> builder()
    {
        return new Builder<>();
    }

    /**
     * Verifies that {@code rowKey}, {@code columnKey} and {@code value} are non-null, and returns a
     * new entry with those values.
     */
    static <R, C, V> Cell<R, C, V> cellOf(R rowKey, C columnKey, V value)
    {
        return Tables.immutableCell(
                checkNotNull(rowKey, "rowKey"),
                checkNotNull(columnKey, "columnKey"),
                checkNotNull(value, "value"));
    }

    /**
     * A builder for creating immutable table instances, especially {@code public static final} tables
     * ("constant tables"). Example:
     *
     * <pre>{@code
     * static final ImmutableTable<Integer, Character, String> SPREADSHEET =
     *     new ImmutableTable.Builder<Integer, Character, String>()
     *         .put(1, 'A', "foo")
     *         .put(1, 'B', "bar")
     *         .put(2, 'A', "baz")
     *         .buildOrThrow();
     * }</pre>
     *
     * <p>By default, the order in which cells are added to the builder determines the iteration
     * ordering of all views in the returned table, with {@link #putAll} following the {@link
     * Table#cellSet()} iteration order. However, if {@link #orderRowsBy} or {@link #orderColumnsBy}
     * is called, the views are sorted by the supplied comparators.
     *
     * <p>For empty or single-cell immutable tables, {@link #of()} and {@link #of(Object, Object,
     * Object)} are even more convenient.
     *
     * <p>Builder instances can be reused - it is safe to call {@link #buildOrThrow} multiple times to
     * build multiple tables in series. Each table is a superset of the tables created before it.
     *
     * @since 11.0
     */
    @DoNotMock
    public static final class Builder<R, C, V>
    {
        private final List<Cell<R, C, V>> cells = Lists.newArrayList();
        @CheckForNull
        private Comparator<? super R> rowComparator;
        @CheckForNull
        private Comparator<? super C> columnComparator;

        /**
         * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
         * ImmutableTable#builder}.
         */
        public Builder()
        {
        }

        /**
         * Specifies the ordering of the generated table's rows.
         */
        @CanIgnoreReturnValue
        public Builder<R, C, V> orderRowsBy(Comparator<? super R> rowComparator)
        {
            this.rowComparator = checkNotNull(rowComparator, "rowComparator");
            return this;
        }

        /**
         * Specifies the ordering of the generated table's columns.
         */
        @CanIgnoreReturnValue
        public Builder<R, C, V> orderColumnsBy(Comparator<? super C> columnComparator)
        {
            this.columnComparator = checkNotNull(columnComparator, "columnComparator");
            return this;
        }

        /**
         * Associates the ({@code rowKey}, {@code columnKey}) pair with {@code value} in the built
         * table. Duplicate key pairs are not allowed and will cause {@link #build} to fail.
         */
        @CanIgnoreReturnValue
        public Builder<R, C, V> put(R rowKey, C columnKey, V value)
        {
            cells.add(cellOf(rowKey, columnKey, value));
            return this;
        }

        /**
         * Adds the given {@code cell} to the table, making it immutable if necessary. Duplicate key
         * pairs are not allowed and will cause {@link #build} to fail.
         */
        @CanIgnoreReturnValue
        public Builder<R, C, V> put(Cell<? extends R, ? extends C, ? extends V> cell)
        {
            if (cell instanceof Tables.ImmutableCell)
            {
                checkNotNull(cell.getRowKey(), "row");
                checkNotNull(cell.getColumnKey(), "column");
                checkNotNull(cell.getValue(), "value");
                @SuppressWarnings("unchecked") // all supported methods are covariant
                Cell<R, C, V> immutableCell = (Cell<R, C, V>) cell;
                cells.add(immutableCell);
            }
            else
            {
                put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
            }
            return this;
        }

        /**
         * Associates all of the given table's keys and values in the built table. Duplicate row key
         * column key pairs are not allowed, and will cause {@link #build} to fail.
         *
         * @throws NullPointerException if any key or value in {@code table} is null
         */
        @CanIgnoreReturnValue
        public Builder<R, C, V> putAll(Table<? extends R, ? extends C, ? extends V> table)
        {
            for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet())
            {
                put(cell);
            }
            return this;
        }

        @CanIgnoreReturnValue
        Builder<R, C, V> combine(Builder<R, C, V> other)
        {
            this.cells.addAll(other.cells);
            return this;
        }

        /**
         * Returns a newly-created immutable table.
         *
         * <p>Prefer the equivalent method {@link #buildOrThrow()} to make it explicit that the method
         * will throw an exception if there are duplicate key pairs. The {@code build()} method will
         * soon be deprecated.
         *
         * @throws IllegalArgumentException if duplicate key pairs were added
         */
        public ImmutableTable<R, C, V> build()
        {
            return buildOrThrow();
        }

        /**
         * Returns a newly-created immutable table, or throws an exception if duplicate key pairs were
         * added.
         *
         * @throws IllegalArgumentException if duplicate key pairs were added
         * @since 31.0
         */
        public ImmutableTable<R, C, V> buildOrThrow()
        {
            int size = cells.size();
            switch (size)
            {
                case 0:
                    return of();
                case 1:
                    return new SingletonImmutableTable<>(Iterables.getOnlyElement(cells));
                default:
                    return RegularImmutableTable.forCells(cells, rowComparator, columnComparator);
            }
        }
    }

    ImmutableTable()
    {
    }

    @Override
    public ImmutableSet<Cell<R, C, V>> cellSet()
    {
        return (ImmutableSet<Cell<R, C, V>>) super.cellSet();
    }

    @Override
    abstract ImmutableSet<Cell<R, C, V>> createCellSet();

    @Override
    final UnmodifiableIterator<Cell<R, C, V>> cellIterator()
    {
        throw new AssertionError("should never be called");
    }

    @Override
    final Spliterator<Cell<R, C, V>> cellSpliterator()
    {
        throw new AssertionError("should never be called");
    }

    @Override
    public ImmutableCollection<V> values()
    {
        return (ImmutableCollection<V>) super.values();
    }

    @Override
    abstract ImmutableCollection<V> createValues();

    @Override
    final Iterator<V> valuesIterator()
    {
        throw new AssertionError("should never be called");
    }

    /**
     * {@inheritDoc}
     *
     * @throws NullPointerException if {@code columnKey} is {@code null}
     */
    @Override
    public ImmutableMap<R, V> column(C columnKey)
    {
        checkNotNull(columnKey, "columnKey");
        return MoreObjects.firstNonNull(
                (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.<R, V>of());
    }

    @Override
    public ImmutableSet<C> columnKeySet()
    {
        return columnMap().keySet();
    }

    /**
     * {@inheritDoc}
     *
     * <p>The value {@code Map<R, V>} instances in the returned map are {@link ImmutableMap} instances
     * as well.
     */
    @Override
    public abstract ImmutableMap<C, Map<R, V>> columnMap();

    /**
     * {@inheritDoc}
     *
     * @throws NullPointerException if {@code rowKey} is {@code null}
     */
    @Override
    public ImmutableMap<C, V> row(R rowKey)
    {
        checkNotNull(rowKey, "rowKey");
        return MoreObjects.firstNonNull(
                (ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.<C, V>of());
    }

    @Override
    public ImmutableSet<R> rowKeySet()
    {
        return rowMap().keySet();
    }

    /**
     * {@inheritDoc}
     *
     * <p>The value {@code Map<C, V>} instances in the returned map are {@link ImmutableMap} instances
     * as well.
     */
    @Override
    public abstract ImmutableMap<R, Map<C, V>> rowMap();

    @Override
    public boolean contains(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
    {
        return get(rowKey, columnKey) != null;
    }

    @Override
    public boolean containsValue(@CheckForNull Object value)
    {
        return values().contains(value);
    }

    /**
     * Guaranteed to throw an exception and leave the table unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final void clear()
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the table unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    @CheckForNull
    public final V put(R rowKey, C columnKey, V value)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the table unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final void putAll(Table<? extends R, ? extends C, ? extends V> table)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the table unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    @CheckForNull
    public final V remove(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Creates the common serialized form for this table.
     */
    abstract SerializedForm createSerializedForm();

    /**
     * Serialized type for all ImmutableTable instances. It captures the logical contents and
     * preserves iteration order of all views.
     */
    static final class SerializedForm implements Serializable
    {
        private final Object[] rowKeys;
        private final Object[] columnKeys;

        private final Object[] cellValues;
        private final int[] cellRowIndices;
        private final int[] cellColumnIndices;

        private SerializedForm(
                Object[] rowKeys,
                Object[] columnKeys,
                Object[] cellValues,
                int[] cellRowIndices,
                int[] cellColumnIndices)
        {
            this.rowKeys = rowKeys;
            this.columnKeys = columnKeys;
            this.cellValues = cellValues;
            this.cellRowIndices = cellRowIndices;
            this.cellColumnIndices = cellColumnIndices;
        }

        static SerializedForm create(
                ImmutableTable<?, ?, ?> table, int[] cellRowIndices, int[] cellColumnIndices)
        {
            return new SerializedForm(
                    table.rowKeySet().toArray(),
                    table.columnKeySet().toArray(),
                    table.values().toArray(),
                    cellRowIndices,
                    cellColumnIndices);
        }

        Object readResolve()
        {
            if (cellValues.length == 0)
            {
                return of();
            }
            if (cellValues.length == 1)
            {
                return of(rowKeys[0], columnKeys[0], cellValues[0]);
            }
            ImmutableList.Builder<Cell<Object, Object, Object>> cellListBuilder =
                    new ImmutableList.Builder<>(cellValues.length);
            for (int i = 0; i < cellValues.length; i++)
            {
                cellListBuilder.add(
                        cellOf(rowKeys[cellRowIndices[i]], columnKeys[cellColumnIndices[i]], cellValues[i]));
            }
            return RegularImmutableTable.forOrderedComponents(
                    cellListBuilder.build(), ImmutableSet.copyOf(rowKeys), ImmutableSet.copyOf(columnKeys));
        }

        private static final long serialVersionUID = 0;
    }

    final Object writeReplace()
    {
        return createSerializedForm();
    }
}
